The main problem is that the game is not rewarding enough for casual players. Not only that you gain much less XP/AP/CP, but with the removal of camps you have to ride for hours (this is no joke) before finding a fight and if you die, you'll ride for hours again. On the other hand you can be killed faster than in an egoshooter, no matter if you ASSIST or not, you get killed too fast, while in a zerg you'll have your healers (remaining templars) and generally "dumb" people, who can follow a shepard but who will never be able to just play "free pvp" and that form of pvp is dissolving like the fog

That is why playing in a zerg gives you more profit and the "being where the action is".. Actually, also the damage is out of control and the game is generally not so interesting for the casual player. It is not "transparent" (you can not understand everything, the game maker does not offer "all" informations, how this game functions).
For me, ESO is quickly loosing any form of casual / small team action and without any random players, also the zergers will vanish, sooner or later,

To Assist you can use some skills that "mark" the target. That is a Nightblades skill or a templars skill BUt as I said, targets die in seconds, literally in seconds